The Sensitive Properties of Hydrate Reservoirs Based on Seismic Stereoscopic Detection Technology

Abstract

Higher‐precision determinations of hydrate reservoirs, hydrate saturation levels and storage estimations are important for guaranteeing the ability to continuously research, develop and utilize natural gas hydrate resources in China. With seismic stereoscopic detection technology, which fully combines the advantages of different seismic detection models, hydrate formation layers can be observed with multiangle, wide‐azimuth, wide‐band data with a high precision. This technique provides more reliable data for analyzing the distribution characteristics of gas hydrate reservoirs, establishing velocity models, and studying the hydrate‐sensitive properties of petrophysical parameters; these data are of great significance for the exploration and development of natural gas hydrate resources. Based on a velocity model obtained from the analysis of horizontal streamer velocity data in the hydrate‐bearing area of the Shenhu Sea, this paper uses three VCs (longitudinal spacing of 25 m) and four OBSs (transverse spacing of 200 m) to jointly detect seismic datasets consisting of wave points based on an inversion of traveltime imaging sections. Accordingly, by comparing the differences between the seismic phases in the original data and the forward‐modeled seismic phases, multiangle coverage constraint corrections are applied to the initial velocity model, and the initial model is further optimized, thereby improving the imaging quality of the streamer data. Petrophysical elastic parameters are the physical parameters that are most directly and closely related to rock formations and reservoir physical properties. Based on the optimized velocity model, the rock elastic hydrate‐sensitive parameters of the hydrate reservoirs in the study area are inverted, and the sensitivities of the petrophysical parameters to natural gas hydrates are investigated. According to an analysis of the inversion results obtained from these sensitive parameters, λρ, Vp and λμ are simultaneously controlled by the bulk modulus and shear modulus, while Vs and μρ are controlled only by the shear modulus, and the latter two parameters are less sensitive to hydrate‐bearing layers. The bulk modulus is speculated to be more sensitive than the shear modulus to hydrates. In other words, estimating the specific gravity of the shear modulus among the combined parameters can affect the results from the combined elastic parameters regarding hydrate reservoirs.

Numerical Investigation of Depressurization through Horizontal Wells in Methane-Hydrate-Bearing Sediments Considering Sand Production

“…Due to symmetry, a two-dimensional x-z plane is simulated. The horizontal wellbore is location at x = 0 m and z = 25 m. The parameters in the model are based on several published datasets [12,13,49]. In the base case, essential simulation parameters are documented in Table 1.…”

“…rameters in the model are based on several published datasets [12,13,49]. In the base case, essential simulation parameters are documented in Table 1.…”

Numerical Investigation of the Gas Production Efficiency and Induced Geomechanical Responses in Marine Methane Hydrate-Bearing Sediments Exploited by Depressurization through Hydraulic Fractures

“…On the basis of the fully coupled thermal–hydraulic–mechanical–chemical model, depressurization in one hydraulic fracture is simulated in a synthetic marine methane hydrate-bearing reservoir. The thermodynamic, rock physical, and rock mechanical parameters are collected from published data targeting a production site in the South China Sea. , Figure describes the conceptual depressurization scenario in the methane hydrate-bearing sediments where a single fracture (base case) and two fractures are stimulated from a horizontal wellbore in the center of a target reservoir with a size of 50 m × 50 m × 50 m. A horizontal 2D plane crossing the wellbore and intersecting the vertical hydraulic fracture plane shown in the figure is used as the domain for the coupled simulation conducted in this work. After stimulation, the hydraulic fracture is established as a high-permeability channel connecting the wellbore and the unfractured sediments.…”

Prospects of Using Gas Hydrates in Power Plants

“…Gas hydrates can be detected by hydroacoustic survey, seismic sounding, geophysical measurements, and electromagnetic exploration [12][13][14]. The most popular method of hydrate detection on the seabed and ocean floor is standard and high-frequency seismic exploration [13,15]. Seismic surveys can be two-dimensional (2D) and three-dimensional (3D) [16].…”